For $$, Hyperion, Mega Power and Bantam are very good.
For $, china brands (eg: Imax B6) are ok to use too. (but mine broke down after 1/2 yr with normal usage)
The silverback 1s uses banana plugs, so make sure your charger has that. If not, you can easily make an adpater (ie t-plug to banana). Just make sure you plug in +'ve and -'ve correctly.
1s lipo do not need to balance charge, so most lipo chargers can support it. of course high-grade chargers can peak the battery better than the cheaper ones.
No ar. With lower A charging, it produce less heat so better for battery and charger, but takes more time. It should charge about the same capacity than fast charging.